They usually grow a fair few leaves before flowering - mine flower from mid June onwards, roughly, though it varies, sometimes its the end of June. The only thing is, if they're in rich and fertile soil, they tend to grow much more foliage and either hardly any, or none at all, flowers - they flower best in poor soil.

The best I ever saw were flowering on a building site in Madeira......it looked all rubble but the site was literally covered in flowers......beautiful.

I love nasturtiums, but mine always get covered in blackfly, so I don't often grow them.

I like them because they attract cabbage white butterflies and while they're chomping nasturtiums they aren't eating the brassicas...Mine aren 't anywhere near flowering yet.